The invention relates to a method for the manufacture of a wire electrode for the spark-erosion process and a wire electrode for this method, which consists of a core of steel, an intermediate layer of copper or a high copper-containing alloy, and an outer layer with at least 40% zinc.
Wire electrodes, which are designed with multiple layers, which have a core of steel, an intermediate layer of copper arranged around the core, and an outer zinc-containing layer, are known, for example, from the DE-PS 29 06 245. All known wire electrodes, which are constructed with a steel core, do indeed have an increased strength compared with copper or brass electrodes, however, all of these erosion electrodes have the disadvantage that if they have comparatively high strengths, their electrical conductivity is very low and merely reaches 8 Sxc2x7m/m2. This comparatively high tensile strength is particularly advantageous for the cutting of high or thick workpieces or, however, also for the cutting of very small parts since high wire tensions are here demanded. However, these known wire electrodes have the disadvantage that their erosion performance is relatively low. In particular, in the case of cutting very small parts with erosion-wire diameters of up to 10 xcexcm, high wire strengths are demanded in order to reduce deflection and vibration of the wire to a minimum. Tungsten or molybdenum wires have been used up to now for the cutting of very small parts with wire thicknesses of 100 xcexcm and less, however, tungsten or molybdenum wires are extremely expensive to manufacture. Erosion wires with a steel core and a brass outer layer have been unable to be successful up to now for this purpose since they always, in comparison to tungsten wires, showed a lesser strength and a poorer erosion behaviour.
The basic purpose of the invention is to provide high-strength erosion electrodes with a core of steel of the abovementioned type and a method for their manufacture, which electrodes have strengths which are 1800 N/mm2 and higher and, in addition, have a comparatively high conductivity of 10 Sxc2x7m/mm2 and more.